Fluidics comparison between dual pneumatic and spring return high-speed vitrectomy systems.

BACKGROUND AND OBJECTIVE: To compare the water and vitreous flow rates and duty cycle (DC) between two ultrahigh-speed vitrectomy systems: pneumatic with spring return (SR) and dual pneumatic (DP) probes. MATERIALS AND METHODS: The flow rate was calculated using a high-sampling precision balance that measured the mass of water and vitreous removed from a vial by a vitreous cutter. Frame-by-frame analysis of a high-speed video of the cutter was used to determine the DC. Three cutters of each gauge (20, 23, and 25 G) were tested with an SR and a DP system using the standard DC setting (biased open) at 0 (water only), 1,000, 2,000, 3,000, 4,000, and 5,000 cuts per minute (CPM) with aspiration levels of 100, 200, 300, 400, 500, and 600 mm Hg. RESULTS: The DC was slightly higher with the SR system using most parameters and gauges although without statistical significance. The water flow rate was somewhat higher with the SR system, except for 25 G with 4,000 and 5,000 CPM. The vitreous flow rate was similar using most parameters, with the SR system showing higher flows at lower cut rates (1,000-3,000 CPM). CONCLUSIONS: SR and DP systems produced similar water and vitreous flow rates. Additional studies in human eyes are necessary to confirm these findings.